Process for the saccharification of wood



Patented Mar. 3, 1931 UNITED STATES PATENT OFFICE EDUARD FARBER,GREGOIRE MINKOFF, AND THOMAS W. M. POND, OF GENEVA, SWIT- ZERLAND,ASSIGNORS TO THE INTERNATIONAL SUGAR AND ALCOHOL COMPANY LIMITED, OFLONDON, ENGLAND, A BRITISH COMPANY PROCESS FOR THE SACCHARIFICATION OFWOOD No Drawing. Application filed June 16, 1927, Serial No. 199,397,and in Germany July 7, 1926.

.ture with a highly concentrated mineral acid i. e. converted intosoluble compounds, and these substances have been converted into sugarby heating them with a very dilute acid under pressure.

According to one known process saw dust was treated with an excess of,for example, 40% hydrochloric acid in the proportion of about 100 partsof wood to 700-1000 parts of hydrochloric acid. The treatment waseffected in a battery of diffusers in which the saw dust remainedincontact with the highly concentrated hydrochloric acid until thesaccharification was completed. Thereupon the wood sugar solution wasseparated from the insoluble residue by displacement with 40%hydrochloric acid.

In another known process hydrochloric acid gas was used in addition tothe highly concentrated hydrochloric acid whereby the quantity of liquidhydrochloric acid employed was considerably reduced. The saw dust wassaccharified by moistening 100 parts thereof with 70100 parts of 40%hydrochloric acid and then the mass was enriched with about 20 partshydrochloric acid gas. By this method the saw dust was first intimatelymixed with strong hydrochloric acid and some hydrochloric acid gas(first stage of the process). The saccharification of the moist mixturewas eifected, preferably in thin layers, whilst the addition of the mainquantity of hydrochloric acid gas was effected in a second stage, of theprocess when the saccharification had been completed; then, afterdriving off the main quantity of hydrochloric acid in a third stage, theresultant wood sugar was dissolved out.

By the present invention these known processes are improved in manyrespects. The use of 40% hydrochloric acid is retained to a certainextent and the process is carried out with less hydrochloric acid gas,with smaller apparatus and in two stages. This is rendered possible bycombining the last portionof the saccharification with the separation ofthe sugar solution from the solid residue. The separation and washingare effected simultaneously by means of hydrochloric acid of which theconcentration is less than that of the hydrochloric used originally, theamount thereof depending upon the manner in which the previous work wascarried out.

Differently stated, according to the new process such quantities ofprimarily applied highly concentrated hydrochloric acid together withhydrochloric acid gas are employed as sufiice to chemically change onlya portion of the cellulose present. The weaker hydrochloric acidsubsequently applied dissolves and hydrolizes then only the remainingunchanged cellulose. The second step in the acid reaction has here quiteanother purpose than in known processes and accordingly the workingconditions are also quite different. Also the weaker hydrochloric acidapplied in the second step must still be a fairly concentratedhydrochloric acid (over 35%). Its reaction also takes place without theaddition of heat or increase of pressure.

parts of saw dust and 40-00 parts of 40% hydrochloric acid and 15 partsof hydrochloric acid gas. With these proportions the wood massn'ioistencd with the acid absorbs the hydrochloric acid gas from astream of gas diluted with air so that the important advantage isobtained of being able to use'dilutod hydrogen chloride. After the woodacid mixture has absorbed the given quantity of hydrochloric acid gas itis conducted directly into a diffusion battery where without agitationit is allowed to stand for a time. By reason of the use of a smallquantity of hydrochloric acid gas the saccharification cannot becompleted freely. If now however fairly concentrated liquid hydrochloricacid acts thereon the breaking up is completed. This part of thesaccharification is carried out as stated simultaneously with theremoval of the sugar solution in the diffusion battery.

The more hydrochloric acid that is used in the first stage the moredilute may be the acids used at the conclusion in the diffusion battery.

111 the improved method of carrying out the diffusion operation, anincrease in concentration of the acid last admitted takes place in thebattery from the material rich in hydrochloric acid which is introducedinto the diffusers so that the saccharification can be completed.

Method of emecution.0n 100 parts sawdust parts highly concentrated (i.e. 40%) hydrochloric acid and 15 parts hydrochloric acid gas are allowedto react. After some hours a third of the cellulose of the wood hasentered into solution and split up into sugar. The portion of celluloseremaining in the wood is now completely converted into sugar by means of38% hydrochloric acid, the latter serving at the same time to separatethe sugar from the solid residue. The temperature may be between 15 and25 C. Increased pressure need not be applied.

In comparison with the difiusion operation refered to in theintroduction of this specification with wood which has not beenpreviously treated and without the addition of hydrochloric acid gas,the present invention presents the advantage that a smaller diffusionbattery serves for the same output or that with a battery of the samesize a larger output may be obtained. As a portion of the actualsaccharification takes place during the preliminary treatment a muchshorter duration of diffusion battery treatment is now required; in factaccording to the new. process 10-12 diffusers can'be'recharged andemptied within 24 hours whereas the output was previously limited to 4-6diffusers. A further advantage is obtained from the economy inhydrochloric acid because, as has been stated above, it is possiblebesides 40% hydrochloric acid to'use also hydrochloric acid of lowerconcentration and diluted hydrochloric acid gas, which are both producedin the manufacture of 40% hydrochloric acid.

What we claim is 1. A process of converting wood into sugar consistingin first treating about 100 parts of sawdust with about 50 parts of 40%hydrochloric acid and about 15 parts of hydrochloric acid gas, and thencompleting the conversion by transferring to a diffusion battery,allowing to stand without agitation, then adding hydrochloric acid ofabout 38% con- Y centration, and simultaneously withdrawing the sugarsolution.

2. A process of converting wood into sugar consisting in first treatingabout 100 parts of sawdust with about 50 parts of 40% hydrochloric acidand about 15 parts of hydrochloric acid gas, and at ordinary pressure,and then completing the conversion by transferring to a diffusionbattery, allowing to stand without agitation, then adding hydrochloricacid of about 38% concentration, and simultaneously withdrawing thesugar solution.

3. A process of converting wood into sugar consisting in first treatingabout 100 parts of sawdust with about 50 parts of 40% hydrochloric acidand about 15 parts of hydrochloric acid gas, and at a temperatureranging between 15 C. and 25 (1, and then co1npleting the conversion bytransferring to a diffusion battery, allowing to stand withoutagitation, then adding hydrochloric acid of about 38% concentration, andsimultaneously withdrawing the sugar solution.

4. A process of converting wood into sugar consisting in first treatingabout 100 parts of sawdust with about 50 parts of 40% hydrochloric'acidand about 15 parts of hydrochloric acid gas, and at ordinary pressureand a temperature ranging between 15. C. and 25 0., and then completingthe conversion by transferring to a diffusion battery, allowing to standwithout agitation, then adding hydrochloric acid of about 38%concentration, and simultaneously withdrawing the sugar solution.

5. A process of converting wood into sugar consisting in first treatingthe wood with concentrated hydrochloric acid and hydrochloric acid gasin quantities insufficient to effect the complete conversion into sugar,and then transferring to a difiusion battery, allowing to stand withoutagitation, then completing the conversion by treatment with hydrochloricacid of concentration less than that of the first mentioned acid butover 35% concentration, and simultaneously withdrawing the sugarsolution.

6. A process of converting wood into sugar, consisting in first treatingthe wood with hydrochloric acid of about 40% concentration andhydrochloric acid gas in quantities insufficient to effect the completeconversion into sugar,and then transferring to a diffusion battery,allowing to stand without agitation,then completing the conversion bytreatment with hydrochloric acid of less than 40% concentration butgreater than 35% concentration, and simultaneously withdrawing the sugarsolution.

7. A process of converting wood into sugar, consisting in first treatingthe wood with hydrochloric acid of about 40% concentration andhydrochloric acid gas in quantities insufficient to effect the completeconversion into sugar, and then transferring to a diffusion battery,allowing to stand without agitation, then completing the conversion bytreatment at ordinary pressure with. hydrochloric acid of less than 40%concentration but greater than 35% concentration, and simultaneouslvwithdrawing the sugar solution. 0

8. A process of converting wood into sugar, consisting in first treatingthe wood with hydrochloric acid of about 40% concentration andhydrochloric acid gas in quantities insuificient to efiect the completeconversion into sugar, and then transferring to a diifusion battery,allowing to stand without agitation, then completing the conversion bytreatment at a temperature ranging between 15 C. and 25 C. withhydrochloric acid of less than 40% concentration but greater than 35%concentration, and simultaneously withdrawing the sugar solution.

9. A process of converting wood into sugar, consisting in first treatingthe wood with hydrochloric acid of about 40% concentration andhydrochloric acid gas in quantities insufiicient to effect the completeconversion into sugar, and then transferring to a difli'usion battery,allowing to stand without agitation, then completing the conversion bytreatment at ordmary pressure and a temperature ranging beteen 15 C. and25 C. with hydrochloric acid of less than 40% concentration but greaterthan 35% concentration, and simultaneously withdrawing the sugarsolution.

In testimony whereof we have signed our names to this specification.

EDUARD FARBER. GREGOIRE MINKOFF. THOMAS POND.

